Chemical vapor deposition processes (CVD) are used to deposit non-conductive and conductive films on a variety of substrates. The chemical CVD process has been enhanced by the use of plasma. This process is referred to as plasma enhanced chemical vapor deposition (PECVD). This PECVD process is commonly used in industrial applications.
PECVD systems are typically driven by high power supplies including microwave, high frequency, very high frequency and radio frequency power supplies. The characteristics of thin films produced by a PECVD process vary substantially and can be controlled by varying the power supply type, the power supply output, carrier gas flow rates, precursor gas flow rates, partial pressure of gases, and substrate pre-conditioning. By varying these parameters, films of different chemistries and thicknesses can be created.
Typical PECVD systems include a plurality of sources, also referred to as antennae, anode or cathose typically fixed in a plane. Each of these antennae are connected to a power supply and emit electromagnetic radiation or create electromagnetic fields producing electrons that are used to generate a plasma in the PECVD process. These antennae are typically arranged in a single plane and are used to deposit thin films on flat substrates. This planar array of antennas tends to result in a homogenous film and an even thickness for smaller substrates.
Unfortunately, this planar antennae array tends to be ineffective for curved substrates and large planar substrates. For example, current PECVD systems have difficulty in controlling gas pressure and gas flows around the edges of large substrates. This control difficulty results in uneven concentrations of carrier gas and precursor gas across the substrate surface—with lower concentrations near the edges. For example, typical PECVD systems pump excess gas and waste materials away from the substrate surface. Typically, this waste gas is pumped from behind the substrate—meaning that the flow of waste gas travels along the surface of the substrate and around the edges. For large substrates the gas concentrates at these edges and can dramatically change the film properties and deposition rates at the edges. Accordingly, a system and method are needed to better control PECVD processes and produce more uniform films.